REPORT OF CAPT. GEORGE B. M^CLELLAN. 331 



If there is behind the chain of videttes a place across which communication is difBciilt, it is best 

 to place the main guards or pickets near it, that they may hold the crossings, and permit the 

 fulfilment of the other conditions for a good arrangement. 



§417. Pickets relieving videttes should always be composed of the same kind of troops as their 

 videttes ; the main guards and reserves are composed according to the nature of the ground 

 between the pickets and the camp ; in places suitable for cavalry they consist of that arm, in 

 defensive positions they are of infantry. 



§418. To secure their greater independence the reserves of the outposts may sometimes be 

 composed of all three arms ; but in an open, unobstructed country they may be of cavalry and 

 horse artillery alone. 



§419. Example of the arrangement of outposts composed of cavalry alone, Plate 6. 



It is supposed that an advanced guard, consisting of a brigade of cavalry and a division of 

 infantry, is in the village A, and that it is necessary to guard it against the enemy, expected 

 by the roads B. 



§ 420. To determine the line of observation to be occupied by the outposts, the whole ground 

 between the position of the advanced guard and the points accessible by the enemy must first be 

 carefully examined on the map ; from the selection of the line of observation results the com- 

 position of the chain and its supports. 



§421. In this example, according to the conditions already mentioned, the most advantageous 

 line of observation is that proceeding from the village L, through the villages M and N, thence 

 following the ridge to the lake P. This line is favorable, because: 



1. The right flank, resting on the marsh near the village L, cannot be turned, and requires 

 no further extension. 



2. The left flank, resting on the lake, allows us to observe from the ridge the distant movements 

 of the enemy ; the ridge also conceals our own movements from the enemy in that direction. 



3. Without being too far ofi", the chain is at such a distance that every movement of the enemy 

 can be discovered in season to enable the advanced guard to take all its measures for operating 

 against him. 



§ 422. Upon the nature of the ground over which the line of observation extends must depend 

 the kind of troops who are to hold it. 



In this example, from the appearance of the ground towards the enemy and towards the advanced 

 guard, it seems that cavalry can act with advantage'; therefore all the outposts are of that arm. 



The extent of the line is a little more than 5 miles, therefore, according to the estimate in § 193, 

 6 companies will be required for the videttes, pickets, and main guards. As the ground opposes 

 no obstacles to the action of cavalry, the reserve should also be of that arm. This reserve, 

 consisting of 4 companies of cavalry and 2 pieces of horse artillery, is posted at the central 

 point C, whence it can easily move to all parts of the outposts. 



§ 423. In accordance with the principles just explained, the commander of the advanced guard 

 issues in this case instructions to the following purport : 



1. The N'" regiment of cavalry and 2 pieces of the N'" battery of horse artillery are detailed 

 for outpost duty. These troops will post a chain of videttes from the village L, through the 

 villages M and N, and along the ridge to the lake P. 



2. Patrols will be sent out : from the village L to F ; from the picket E'", along the road G ; 

 and from the other posts, in the direction in which the enemy is expected. 



3. If the enemy attacks in force, the outposts will fall back upon the advanced guard. 



With these instructions as a basis, the commander of the outposts makes his assignments ; 



